The present invention relates to genetic engineering, and in particular to nucleotide sequences encoding enzymes for catalyzing the biosynthesis of carotenoids, such as zeta-carotene.
Carotenoids are 40-carbon terpenoids having eight connected isoprene units. Carotenoids include phytoene, zeta-carotene, lycopene, beta-carotene, zeaxanthin and zeaxanthin diglucoside. See Krinsky et al., Carotenoids: Chemistry and Biology, Plenum Press, pp. 279-291 (1990) and Nes et al., Regulation of Isopentenoid Metabolism, ACS Sym. Ser. 497 (1992). A biosynthetic pathway for the various carotenoids is set forth in European Patent Application No. 393,690, U.S. Pat. No. 5,304,478 and PCT WO 91/13078, which are incorporated herein by reference.
Certain carotenoids can be considered intermediates in the biosynthetic pathway of other carotenoids. However, carotenoids such as phytoene have been found to have a useful application in absorbing ultraviolet radiation. See U.S. Pat. No. 4,642,318. Furthermore, the carotenoid lycopene, has been found to have use as a coloring agent in situations in which a red color is desired. See Taylor, Carotenoids: Products, Applications and Markets, Decision Resources, Inc. (1990). Other biosynthetically produced carotenoids have found use as coloring agents, particularly for foods, in situations in which an orange or yellow color is desired. Carotenoids also have been found to be useful as animal feeds, as well as in the pharmaceutical and cosmetics industries. See Taylor, Carotenoids: Products, Applications and Markets, Decision Resources, Inc. (1990), and E-Siong Tee, Crit. Rev. Food Sci and Nutri., Vol. 31, p.103 (1992) .
It would be highly desirable to have the capability of altering the biosynthetic pathway for carotenoids, particularly in higher plants such as the solanaceae. As such, it would be desirable to provide nucleotide sequences that encode enzymes useful in the carotenoid biosynthesis pathway, such as phytoene desaturase. In particular, it would be desirable to provide the nucleotide sequences that encode phytoene desaturase from a higher plant species, such as a Nicotiana species.